U.S. Pat. No. 4,270,562 which issued to Oberth, et al. on June 2, 1981 illustrates a lubrication system for relatively large engines. In such engines, it is desirable to prelube the engine, i.e. to force the lubrication of the engine prior to startup so that certain components such as the crankshaft, connecting rods and the camshaft bearings are properly lubricated. If the bearings are not provided with sufficient lubrication at the initial rotation of the engine, damage of the bearings could occur. Normally, a preestablished time delay prevents the starting circuit from being energized until prelube has been accomplished. For example, due to the size of the larger engines it may require several minutes to pump lubricating fluid to the bearings by way of the various engine galleries and passages.
Engines used to power standby generators or the like, must be started in a matter of seconds in order to respond to an emergency. Prelube for these engines is accomplished by continually pumping lubrication fluid to the bearings of the crankshaft, camshaft and rocker arms, and this permits the engine to be started without delay.
Typical prior art prelube systems have an electric or air driven pump separate from the main engine pump that supplies lubrication fluid to the engine when the engine is not running. Starting of the engine where the prelube pump has failed, whether by a loss of power to drive the pump or a problem with the pump itself, could result in a drastic reduction in the service life of the engine.
During long periods of continuous prelube, where the engine has not run for a considerable amount of time, lubricating fluid being pumped upward into the rocker arm area drips onto the valve mechanism, and can even run down valve guides, past any open valve into one or more of the engine combustion chambers. An accumulation of the incompressible fluid in a combustion chamber while cranking the engine could result in the damage of expensive engine components and require a considerable amount of time to repair.
Accordingly, what is desired is a lubrication system that will prevent lubrication fluid from entering certain elevated portions of an engine such as the rocker arm area, where fluid could otherwise find its way into a combustion chamber, when the engine is not running. The system must not be affected by engine oil temperature, viscosity or a wide range of prelube pump capacities and pressures. Moreover, when the engine is running the system must allow the supply of lubrication fluid to promptly reach the rocker arm area for lubrication of the valve operating mechanism. Also what is desired is a system that allows the engine starting mechanism to be energized solely when it is sensed that there is a sufficient supply of lubrication fluid in the critical areas of the engine, and to prevent the starting mechanism from being energized if there is an insufficient supply.
The present invention is directed to overcoming one or more of the problems as set forth above.